β-tributylstannylacrylates. Stereospecific synthesis via conjugate additon of tributylstaknylcopper

Tetrahedron Letters,Vol.22,No.49,pp Printed in Great Britain

4909-4912,198l

0040-4039/81/494909-04$02.00 01981 Pergamon Press Ltd.

@TRIBUTYLSTANNYLACRYLATES. STERPOSPECIFIC SYNTHESIS VIA CONJUGATE ADDITON OF TRIBUTYLSTAENYLCOPPER David E. Seitz" and Shi-Hung Lee Department of Chemistry Northeastern University Boston, MA 02115 Abstract. The synthesis of cis- and trans-8-tributylstannylacrylates from conjugate addition of tributylstannylcopper to various $-substituted acrylates is shown to be a highly stereospecific reaction. Of four tributylstannylmetal reagents examined for this conversion, optimum results were obtained with tributylstannylcopper. The ability of tin, suitably positioned in an organic molecule, to under1

go a variety of useful transformations (e.g. electrophilic destannylation, transmetalation, 2 oxidative destannylation3) has occasioned considerable

interest in the development of highly stereo- and regiospecific methods for assembling functionalized organostannanes.

For example, investigations in

this laboratory on an electrophile-induced demetalation approach to the synthesis of the y-oxygenated a,B-unsaturated lactone moiety common to a number of biologically active macrocyclic structures, such as brefeldin-A, require cis- and trans-8-tributylstannylacrylates

(,&a,b) as intermediates.

/

‘.

Bus!3 ?+ H

c”,,,

HOw

4

&& bre feldin -A

Although hydrostannation of alkyne derivatives is often a convenient method for securing vinylstannanes, 5 preparation of & via additon of trialkyltin hydrides to esters of propiolic acid yields a mixture of compounds 4909

4910

whose

resolution

undergo esters

smooth

is attended Michael-type

and nitriles relatively

paration

of unsaturated

unsaturated

esters

acetylenic

esters

We report available

to a variety copper(I) for this

the desired

acrylates

conditions

3 and 6 afforded

-78"C,

these

ization competing

The

observed

donor

administered

and required

with

with

are

of these

The

with

Society

Piers.

complete

unreactive isomerof

of a suit-

to carbon-carbon is currently

by the Petroleum

during

The

is a result

destannylation

is gratefully

by Piers7

stereo-

were

in the absence

discussions

3,3-

earlier

temperature.

B-tributylstannylacrylates

helpful

to 2 while methyl

however,

apparently

intermediate 8 by Piers.

Chemical

acknowledge

relative

to that noted

elevated

of this research

cuprate

Bu$nCu

2.1 adduct,

proceeded

via electrophilic

Support

Professor

di(tributylstannyl)-

the latter.

derivatives,

a more

of

examined

($) and tributylstannyl-

of product

a saturated similar

(Qg

5

of the copper

by the American

also warmly

investigation

to give

and phenylthio

and synthesis 11 investigation.

Acknowledgement.

798

reagents

Bu3Sn(PhS)CuLi

of the haloacrylates

formation

authors

obtained

a result

as suggested

The application

under

were

for the trans-phenylthioacrylate

equilibration

able proton

bond

(x), lithium

diminishe d yields

tosyloxy

conditions

cl,@

and

of one equivalent

4

2 appeared

the reaction

specificity. under

in the presence

3

bis(tributylstannyl)propanoate, At

enones

cis- and -.trans-R-tributylstannylacrylates addition of tributylstannyllithium

(Bu BSn)zCuLi

reagent

R-iodo

Of the four tributylstannylmetal

2

the lithium

the syntheses

phenylthio(trimethylstannyl)cuprate.

tributylstannyllithium

Bu$nLi

reagents

described

for the pre-

(Z)-B-trimethylstannyl

tributylstannyl(phenylthio)cuprate

optimum

organostannanes,

are recorded

has

(E)- and

ketones,

stereospecific

(Table).

conversion,

saturated

technique Piers

and

reagents

of a,B-unsaturated

of the corresponding

with

of 8-substituted

(2) ,I0

copper

respectively

($), lithium

cuprate

enones

from reaction

that

iodide

of this

organostannanes.

by the highly

Trialkylstannylmetal

to a variety

the corresponding

few examples

B-trimethylstannyl

6

difficulty.

addition

to provide

however,

of cyclic

with

Research

acknowledged. the course

Fund, The

of this

x

Hx

PhS

H

C02CH3

H

H

Equivalents

1.9

i.5

I.5

2.0

4.3

2.0

Bu3SnCu

(5)

min

00/4

hr,

H

x

x

H

Bu,Sn x

w H’

Bu3Sn

Bu,Sn

H

Bu,Sn

H

Bu,Sn

H

C02CH2CH3

‘H

C02CH3

H

C02CH3

C02CH3

H

*

50

59

47

62

62

58

Yield ’ (%I

and gave satisfactory

Product

asstgned structures

hr, hr

hr

hr, 0°/4hr,

3 hr

wlfh

-78”/1 25”/1

-78O/i 25”/t

-78O/

-78O/40

hr

min

(“Cl/Time

-78Ol2.5

-78740

Temp

a. all compounds exhibited spectral data in full accord combustion analyses. b. all yields refer to isolated purified products. c. product ratto was determined from NMR spectrum.

x

C02CH3

I

H

CO$H3

H

H

C0$H3

CO,CH 3

H

‘x

H

x

Cl

H

Cl

Substrate’

TABLE

4912

References and Notes 1.

For a review, see: M. Pereyre and J.-C. Pommier, J. Organomet. Chem. Libr., 1, 161 (1976). For recent examples, see: D.E. Seitz, G.L. Tonnesen, S. Hellman, R.N. Hanson and S.J. Adelstein, J. Organomet. Chem., ?186, C33 (1980); D.E. Seitz, R.A. Milius and H. El-Wakil, Synthetic Commun., 11, 281 (1981); G.L. Tonnesen, R.N. Hanson and D.E. Seitz, Int. J. Appl. Radiat. Isotopes, 32, 171 (1981).

2.

For a review, see. D.J. Peterson, Organometal. Chem. Rev. A, 7, 325 (1972). For recent examples, see. D.E. Seitz and A. Zapata, Tetrahedron Lett., 3451 (1980); D.E. Seitz and A. Zapata, Synthesis, 557 (1981); D.E. Seitz and A. Zapata, Synthetic Commun., -11, 673 (1981).

3.

W.C. Still, J. Am. Chem. Sot., 99,

4.

For examples, see: K.C. Nicolaou, Tetrahedron, 2, Back, Tetrahedron, 33, 3041 (1977).

5

For reviews, see. W.?. Neumann, "The Organic Chemistry of Tin," John Wiley and Sons, New York, 1970, pp. 96-99; E-i. Negishi, "Organometallics in Organic Synthesis," John Wiley and Sons, New York, 1980, pp. 410-412.

6.

A.J. Leusking, J.W. Marsman, H.A. Budding, J.G. Poltes and G.J.M. van der Kerk, Rec. Trav. Chim., 84, 567 (1965); A.J. Leuskink, H.A. Budding and J.W. Marsman, J. Organomet. Chem., 2, 285 (1967).

7.

E. Piers and H.E. Morton, J. Chem. Sot., Chem. Commun., 1033 (1978).

8.

E. Piers and H.E. Morton, J. Org. Chem., 45, 4263 (1980).

9.

W.C. Still, J. Am. Chem

4836 (1977). 683 (1977); T.G.

Sot., -100, 1481 (1978).

10.

The cuprate (or copper) reagents were prepared by adding a tetrahydrofuran solution of tributylstannyllithium, prepareg from reaction of tributyltin hydride and lithium diisopropylamide, to the required amount of cuprous iodide or phenylthiocopper at -78°C and stirring for ten minutes. The coupling constants observed for the vinyl protons in the cis- and trans-B-tributylstannylacrylates, 13.0 and 19.5 Hz, agree with those reported earlier for a series of related compounds (ref. 6b), The haloacrylates employed in this study were synthesized according to J. Biougne and F. Theron, C.R. Acad. Sci., 272, 858 (1971). Spectral data were in full agreement with those reported. The phenylthioacrylate was secured from reaction of the trans-iodoacrylate with thiophenoxide at -78°C and exhibited a vinyl proton coupling constant of 15.2 Hz. The preparation of the tosyloxyacrylate was modeled after S. Danishefsky, T. Harayama and R.K. Singh, J. Am Chem. Sot., 101, 7008 (1979). This The derivative exhibited a vinyl proton coupling constant of 7.0 HZ. geometrical purity of starting materials and products was deduced from analysis of the 60 MHz proton NMR spectra.

11.

For a detailed discussion of the addition of various trimethylstannylmetal reagents to alkynoates, see: E. Piers, J.M. Chong and H.E. Morton, accompanying communication. (Received in USA 9 June 1981)